(SEM V) THEORY EXAMINATION 2023-24 COMPUTER GRAPHICS

Subject Code: KCS053

Subject Name: Computer Graphics

Course: B.Tech (Semester V)

Maximum Marks: 100

Duration: 3 Hours

Exam Year: 2023–24

Sections: A, B, and C

SECTION A – Short Answer Questions (2 × 10 = 20 Marks)

Attempt all questions briefly.

a. Why is the slope–intercept form commonly used for representing lines in computer graphics?
b. Describe how a point is represented in a computer graphics system.
c. Explain the Bresenham Line Drawing Algorithm briefly.
d. Discuss the significance of parallel versions of line drawing algorithms.
e. How does the Sutherland–Hodgman polygon clipping algorithm work?
f. Discuss the significance of text clipping in graphical applications.
g. What is a projection in the context of 3D viewing?
h. What role do matrices play in 3D transformations?
i. What are blobby objects in computer graphics?
j. What is the significance of specular reflection in rendering?

Tips for Section A:

Revise key algorithms (Bresenham, Sutherland–Hodgman).

Recall matrix transformations (rotation, scaling, translation).

Understand illumination types: diffuse, ambient, specular.

SECTION B – Medium-Length Questions (10 × 3 = 30 Marks)

Attempt any three of the following.

Display Technologies:

Compare Random Scan vs Raster Scan displays.

Random Scan: Vector-based, smooth lines (used in radar, CAD).

Raster Scan: Pixel-based, supports shading and animation.

Midpoint Circle Algorithm:

Uses decision parameter p = 1 - r to plot circles symmetrically in 8 octants.

Advantage: integer arithmetic, no floating-point computation.

Composite Transformations:

Combination of translation, scaling, and rotation.

Represented using matrix multiplication.

Example: moving a rotated and scaled object in a single transformation.

3D Clipping Methods:

Cohen–Sutherland 3D, Liang–Barsky, and Cyrus–Beck methods.

Advantages: fast region codes; drawbacks: computational complexity for arbitrary volumes.

Splines in Graphics:

Smooth curve representations (e.g., B-splines, Bezier curves).

Applications: CAD modeling, animation paths, and design tools.

SECTION C – Long / Analytical Questions (10 × 5 = 50 Marks)

Q3. Display & Graphics Systems

a. Explain the function of a video controller in a graphics system — manages frame buffer, refresh rate, and display timing.
OR
b. Compare Vector Graphics vs Raster Graphics —

Vector: object-based, scalable, no aliasing (e.g., CAD).

Raster: pixel-based, color-rich, used for photos and games.

Q4. Line Drawing Algorithms

a. Compare DDA and Bresenham’s Algorithm —

DDA: uses floating-point; slower.

Bresenham: integer-based; faster and more efficient.
OR
b. Criteria for a good line drawing algorithm: accuracy, efficiency, low computation, smoothness.

Q5. Clipping Algorithms

a. Compare Cohen–Sutherland and Liang–Barsky —

Cohen–Sutherland: uses region codes, efficient for trivial accept/reject.

Liang–Barsky: parametric equations; faster for line clipping.
OR
b. Curve Clipping Techniques: involve subdividing curves into line segments for clipping; challenges include precision and computational load.

Q6. 3D Transformations & Projections

a. Stages of 3D Transformation Pipeline:

Modeling transformation             Viewing transformation

Projection transformation            Clipping and windowing
OR
b. Orthographic vs Perspective Projection:

Orthographic: parallel lines remain parallel.

Perspective: simulates depth; lines converge at vanishing point.

Q7. Hidden Surface & Illumination

a. Compare A-buffer and Z-buffer methods —

Z-buffer: stores depth per pixel; efficient, memory-based.

A-buffer: handles transparency and anti-aliasing.
OR
b. Phong Illumination Model:

Combines ambient, diffuse, and specular reflections.

Used for realistic rendering by calculating intensity per pixel using:

• I=IaKa+IdKd(L⋅N)+IsKs(R⋅V)nI = I_a K_a + I_d K_d (L \cdot N) + I_s K_s (R \cdot V)^nI=Ia​Ka​+Id​Kd​(L⋅N)+Is​Ks​(R⋅V)n

where nnn is the shininess coefficient.

Key Topics to Prepare

Fundamentals

Line and circle algorithms (DDA, Bresenham, Midpoint).

Scan conversion principles.

2D & 3D Transformations

Matrix operations for translation, rotation, scaling, reflection, shear.

Homogeneous coordinates.

Clipping Algorithms

Line: Cohen–Sutherland, Liang–Barsky, Cyrus–Beck. Polygon: Sutherland–Hodgman, Weiler–Atherton.

Curve: parametric and subdivision methods.

3D Viewing & Projection

Orthographic, Perspective, Isometric projections.                Transformation pipeline.

Rendering & Illumination

Shading models: Phong, Gouraud, Flat.       Hidden surface removal (Z-buffer, A-buffer, Painter’s algorithm).

Blobby objects and Ray tracing basics.

Study Tips

Practice diagrams: transformation pipelines, clipping windows, projection types.

Revise mathematical equations (matrix transformations, illumination).

Write pseudocode for Bresenham, Midpoint, and Sutherland–Hodgman algorithms.

Understand differences — DDA vs Bresenham, Raster vs Vector, Orthographic vs Perspective.

Focus on visual clarity — neat labeled diagrams in exam answers fetch high marks.